An electronic throttle control system (ETC) for controlling the amount of air to an engine is well known. The throttle valve plate of the throttle body pivots in response to signals received from the engine control unit (ECU) and thereby acts to regulate the amount of air delivered to the intake manifold. Throttle position and engine load sensors help the ECU maintain the correct throttle position over the range of expected engine torque loads.
Prior art throttle plates are designed to default to a “home” position where the plate is approximately 10–20 degrees to the axis of the throttle bore in which it is pivotally attached. Thus, when an engine is in the engine-off condition, prior art throttle plates are designed to default to the home position which is a slightly open position (e.g., by about 10–20 degrees depending on the particular application) when in the engine-off condition or upon receiving an ETC fault signal. Should the ETC malfunction, some air must be able to reach the intake manifold to allow the car a “limp home” condition for needed repairs. Thus, the prior art typically provides an ETC throttle system with a throttle plate that defaults to a slightly open position in engine-off and ETC failure conditions. However, one problem that has been encountered to this throttle home default position is the throttle plate becoming stuck in the home position due to winter-time ice and/or engine carbon based build up (commonly referred to as engine coke) in this area. In response to this problem, prior art throttles have been designed with a DC brush motor and two stage spur gear train to produce the torque necessary to break the throttle free from ice and/or coke formation. This, however, requires a relatively large amount of space in the throttle housing which is inefficient and costly. There therefore exists a need for an ETC throttle body that gives the engine enough air for a limp home condition yet also provides relatively small, inexpensive components capable of delivering a large amount of torque to free the throttle plate from a stuck position.